As known in the field of computer networking, a load balancer is a physical or virtual network device that (1) intercepts, from clients, network traffic directed to one or more services (e.g., an application, a website, etc.), and (2) distributes that traffic across a cluster of real servers configured to host the services. By intercepting and distributing network traffic in this manner, the load balancer can provide greater service reliability (by, e.g., directing traffic away from failed servers), better service performance (by, e.g., reducing the load on each real server), and greater security (by, e.g., isolating the real servers from the clients).
Generally speaking, the process of enabling load balancing for a particular service in a network environment involves configuring a virtual IP address (VIP) for the service on a load balancer of the environment. This VIP, which is associated with a physical ingress port (or group of ingress ports) of the load balancer, is presented to external clients as the endpoint address of the service. In addition, the process involves associating, on the load balancer, the VIP (and/or the service) with the IP addresses of a number of real servers in the network environment. The real servers are configured to host the service identified by the VIP. With this configuration in place, when a client attempts to access the service using the VIP, the load balancer receives the client request because the VIP points to the load balancer rather than the real servers. The load balancer then applies a load balancing algorithm (e.g., round robin, weighted round robin, etc.) to select a particular real server for handling the request from among the group of real servers associated with the service/VIP and forwards the request, using network address translation, to the selected real server.
In a network environment that comprises a single load balancer, enabling load balancing for a service is straightforward because there is no choice involved in terms of selecting which load balancer will host the service's VIP (and thus will carry out load balancing duties for the service); the service can only be configured on the environment's singular load balancer. However, in network environments that comprise a pool of multiple available load balancers such as a large-scale data center, enabling load balancing for a service involves answering a threshold question of which load balancer in the environment should be configured to handle the traffic for the service. Once a particular load balancer in a pool of available load balancers is selected, the network administrator can perform the tasks of configuring the VIP and real server IP addresses on that selected load balancer as discussed above.
In most multi-load balancer environments today, the question of load balancer selection is typically addressed manually and in an ad-hoc manner by network administrators. For example, a network administrator may select a load balancer at random, or based on the administrator's perception of what the “best” load balancer should be in view of the nature of the service. This manual, ad-hoc approach can lead to inefficient usage of load balancer resources, since the network administrator may select a load balancer that he/she thinks is appropriate, when in fact the selection of a different load balancer may result in, e.g., less resource use, better service performance, etc.
Accordingly, it would be desirable to have a more structured and automated approach for load balancer selection in a multi-load balancer environment that allows for optimized usage of load balancer resources.